The present invention relates to a transfer mask (or a reticle) to be used in a lithography technique for manufacturing a semiconductor device or the like by using a charged particle beam or an electron beam, a mask blank (or a mask forming substrate), and a method for manufacturing the mask.
In order to form a wiring pattern or the like, there has been utilized the lithography technique. As the wiring pattern becomes the finer, the optical lithography technique or a general technique has found it the more difficult to form the pattern. For this difficulty, there has been investigated an exposure technique which uses a charged particle beam such as an electron beam or an ion beam or a short-wavelength beam such as an X-ray for the finer structure.
Of these, the electron beam drawing technique has transferred from the point beam drawing method at the initial stage to the variable shape drawing method for drawing by changing the size and shape of a square beam. After this, from the standpoint of improving the pattern precision and shortening the drawing time period, there has been proposed a partial batch drawing method by which a portion of a pattern is partially drawn in a batch through a mask such that the drawing is repeated. Subsequent to this partial batch drawing method, moreover, a new electron projection system (or the SCALPEL system) was proposed about eight years ago by S. D. Berger and others. After this, there have been made various proposals such as a similar drawing system (or the PREVAIL system) or a transfer mask (or reticle) structure to be applied to those drawing system, and their manufacturing methods. For example, U.S. Pat. No. 5,466,904 relates to the PREVAIL system, as invented by H. C. Pfeiffer and others. This PREVAIL system will be briefly explained. First of all, there is prepared a stencil mask in which a through-hole (or aperture) pattern is formed at each small region in predetermined size and arrangement. The small regions of the stencil mask are irradiated with the charged particle beam to shape the beam according to the through-hole pattern. An exposure substrate having a photosensitive material is irradiated with the shaped beam through an optical system so that the through-hole pattern is transferred in a reduced scale to the exposure substrate. Moreover, the device pattern is formed by jointing the predetermined pattern, as formed separately on the stencil mask, over the exposure substrate.
The transfer mask, as proposed for the PREVAIL system of this kind, has such a stencil type mask for its main structure that the pattern portion is composed of non-shielded through holes. This transfer mask is disclosed in Unexamined Published Japanese Patent Applications Nos. 10-261584 and 10-260523, for example. In the stencil type mask, the deflection of the pattern region is reduced by separating and reinforcing it from the back side with a strut (or bridge) structure. By this, it is intended to improve the pattern positioning precision.
As the mask for the SCALPEL system, on the other hand, there has been mainly proposed a scattering mask (or reticle) than the stencil mask. This scattering mask is disclosed, for example, in a publication (pp. 153, of APPL, PHYS. LETTERS 57(2) (1990), EDITED BY S. D. BERGER and J. M. GIBSON) or Unexamined Published Japanese Patent Applications Nos. 10-261584 and 10-321495. In the mask structure, according to these publications, there is formed over a membrane (or a self-sustaining thin film) of SiN or the like a heavy metal layer, over which a desired pattern is formed. Both these layers are irradiated with the electron beam, but the electron scattering degree is different depending upon whether the electron beam scattering body is present or not. By making use of this difference in the electron scattering degree, a beam contrast on the wafer is obtained to transfer the pattern in a reduced scale.
In the aforementioned exposure system, the high resolution featuring the charged particle ray can be satisfied to form a finer pattern than 0.1 micron. This exposure system is enabled to Improve the throughput in the manufacture of the device by enlarging the shot size drastically, as compared with the partial batch drawing method. When the maximum shot size over the exposure substrate is enlarged from 5 micron to 250 micron, for example, a throughput of 30 sheets/hour or more can be obtained with the minimum line width of 0.08 micron and for an eight-inch substrate. This exposure system has a highly practical system having an ability to produce a general-purpose device.
Thus, there have been made the various proposals including the proposal of the aforementioned new exposure system, the proposal relating to the transfer mask (or reticle) to be applied to that system, and proposal relating to a method for manufacturing the mask. However, the various mask structures thus proposed have several problems from the standpoint of practice. These problems will be cursorily reviewed in the following.
The types of the masks proposed heretofore are coarsely divided into two kinds. The first type is the stencil mask having a pattern of through holes. The second type is the scattering mask in which an electron beam scattering body made of a heavy metal is formed over a thin film transmission layer having a thickness of 100 to 200 nm. In addition, there is a proposal of the mask of the reflection type, the description of which will be omitted. The representative structures of the first and second types are shown in FIGS. 1 and 4, respectively.
As shown in FIG. 1, the transfer pattern portion of the stencil mask has through holes 1. It follows that there is little energy loss of the drawing electrons. Because of the pattern of a high aspect ratio, on the other hand, there is a problem in the pattern sizing precision. Because of the through holes, there is a problem on the mechanical strength of the mask. For these solutions, there is known the technique for improving the working precision and enhancing the mask strength by making the pattern region (or the thin film portion) as thin as possible (e.g., to 2 micron) and by forming struts (or a bridge) (although not shown) on the mask back side for supporting the pattern region (or the pattern field).
Where the transfer pattern has the through holes, however, the ring-shaped (or donut-shaped) pattern or the like cannot be formed in a completely independent form. A solution for this case is disclosed on pp. 210 of Solid State Technology, September (1984), edited by H. Bohlen and others. According to this method, there is prepared a complementary mask for assembling desired structural component patterns so that the pattern is formed by overlaying the complementary patterns. According to this method, however, at least two times as many as masks are required, and the shot number of exposures are increased to invite a drastic elongation of the exposure time period. This lowers the processing ability owned by the exposure system. Another demerit is that a proper pattern division is required for each device pattern. Moreover, a new problem occurs if the pattern region (or the thin film portion) is thinned to improve the working precision (or the pattern sizing precision).
The transfer pattern portion of the stencil mask has through holes. The pattern to be formed at this time raises no special problem if it is only contact holes (FIG. 2A) or a short line pattern (FIG. 2B), as shown in FIGS. 2A and 2B (in which the black portions indicate the through holes). For conveniences of the element pattern design, however, a pattern supporting portion 4 may be a cantilever pattern (as will be called the xe2x80x9cleaf patternxe2x80x9d), as shown in FIGS. 3A and 3B (in which the black portions individually indicate the through holes 1).
in this case, the leaf pattern causes a deflection displacement in the longitudinal direction (i.e., in the normal to the mask face) in dependence upon the conditions. In the fine pattern or the line pattern (having an L and S ratio of 1:1) having a high pattern density; on the other hand, the mechanical strength is lowered in the transverse direction (i.e., in parallel with the mask face). If the material for the aperture body has an extremely large Young""s modulus in this case, it is possible to reduce the deflection displacement. Even if a polycrystalline diamond film having the largest elastic coefficient known at present is applied to the aperture body, however, it is difficult to reduce the deflection displacement to a practical level so long as the sectional area of the pattern supporting portion 4 shrinks.
In the exposure system according to the SCALPEL system or the PREVAIL system, moreover, the mask always acts at a high speed so that a seriously high power in the transverse direction acts upon the aperture pattern (including the leaf pattern), as judged from the microscopic viewpoint in other words, it is important to view the mask rigidity not only in the longitudinal direction but also in the transverse direction (i.e., in parallel with the mask face). On the leaf pattern portion, however, there is caused to act the bending stress or the twisting stress by the high-speed movement of the mask stage so that a stress concentration occurs at the pattern supporting portion 4 of the leaf pattern. It is, therefore, predicted that the pattern breakage occurs.
In the SCALPEL mask (or the electron beam scattering mask), on the other hand, problems of the loss of the transmission electrons and the mask durability are caused by the electron beam scattering at the electron beam transmitting layer (or film) (as will be called the xe2x80x9cpattern supporting layer (or film)xe2x80x9d or the xe2x80x9cmembranexe2x80x9d) by the mask structure.
With reference to FIG. 4, here will be described a sectional structure of the electron beam scattering mask. This electron beam scattering mask retains the contrast by the difference in the electron scattering degree depending upon the presence or absence of an electron beam scattering body 5 and by a limiting aperture. Since the self-sustainment is difficult with only the electron beam scattering body made of a heavy metal, however, a pattern supporting layer 6 has to be formed with a view to supporting the heavy metal scattering layer.
In the mask of this structure, there arise contrary problems of the thickness and the electron transmissivity of the pattern supporting layer 6 for supporting the electron beam scattering layer. As the material for the pattern supporting layer, there is known an SiN group or an Si material, and there is proposed a diamond film or the like. The preferable characteristics required for these pattern supporting layer materials are a low material density and an excellent material strength such as the Young""s modulus. In other words, it can be said that the more excellent electron transmissivity at the pattern supporting layer 6 and the higher elastic modulus of the material are the preferable. From only the viewpoint of the electron transmissivity, the problems can be solved by making the acceleration voltage of the charge particle beam higher and the pattern supporting layer 6 thinner. The acceleration voltage of the electron source to be used in the SCALPEL or the like is as high as 100 KeV. Therefore, the thickness (of 50 to 200 nm) of the pattern supporting layer, as disclosed in U.S. Pat. No. 5,260,151, for example, transmits about 100% of electrons. In any substance, however, the electrons are scattered. The scattered electrons transmit through the pattern supporting layer. Since the electron outgoing angle from the pattern supporting layer is within a predetermined range, however, the electrons having an outgoing angle outside the predetermined range cannot pass through the limiting aperture which is formed in the upper portion of the exposure substrate in the exposure apparatus. This invites a reduction in the ratio of the electrons for the exposure (as will be called the xe2x80x9cexposure electronsxe2x80x9d). In order to reduce the electron number outside the predetermined range, i.e., to increase the electron number to transmit without being scattered, there is no way other than thinning the pattern supporting layer acting as the support.
In the case of the heavy metal scattering body, as exemplified by tungsten, however, a film thickness of about 50 nm is sufficient for retaining several times of electron scatterings. In order to support the scattering body having the thickness of 50 nm, however, an SiN film having a thickness of about 100 to 150 nm is necessary, if set from the viewpoint of the material strength characteristics by applying a pattern supporting layer of the silicon nitride (or the SiN group). If the pattern supporting layer having this film thickness is employed, the exposure electrons at the acceleration voltage of 100 KeV are reduced by about 40 to 50% by the electron scattering in the pattern supporting layer. If the SiN pattern supporting layer is thinned, it is deflected by the own weight of the tungsten scattering body. Moreover, the pattern supporting layer cannot stand many working steps so that it is liable to be broken.
It the electron beam scattering layer of the heavy metal is excessively thin, as described above, a satisfactory beam contrast cannot be obtained. If the electron beam scattering layer of the heavy metal is thickened to establish the satisfactory beam contrast, on the other hand, it is deflected by its own weight, or the film stress change (or the deflection change) is enlarged in the working step so that the breakage is liable to occur. In order to support the heavy metal electron beam scattering layer, on the other hand, the electron beam transmitting layer has to be made considerably thick to raise a problem that the exposure electrons are largely lost. In the SCALPEL mask, moreover, the demands for thinning the individual layers and for retaining the stress are contrary to each other so that the prior art has found it difficult to provide a practical mask.
Where the mask stage is operated at a high speed as in the stencil mask when the mask is employed, moreover, it is predicted that the pattern region (or the thin film portion) including the electron beam scattering body is extremely breakable.
In addition, where the scattering mask made of a electron beam scattering body of a heavy metal is to be applied to the exposure apparatus of the stepper type like the PREVAIL system, not only the reduction in the exposure electrons but also the aberration raises a problem. By the inelastic scattering at the pattern supporting layer, more specifically, the color aberration is caused due to the dispersion of the beam energy to invite a deterioration in the resolution. A countermeasure against this resolution deterioration is not practical in conclusion because the beam current value has to be extremely lowered to invite a drastic elongation of the exposure time period.
Therefore, an object of the present invention is to provide an electron beam drawing mask capable of solving the problems such as the beam contrast, the control of the scattering angle of electrons, the loss of the exposure electrons, the reduction in the color aberration or the shortening of the exposure time period.
Another object of the present invention is to provide an electron beam drawing mask capable of improving the lithography characteristics and manufacturing a superhigh integrated circuit.
Still another object of the present invention is to provide a mask blank for the aforementioned electron beam drawing mask.
A further object of the present invention is to provide a method for manufacturing the aforementioned electron beam drawing mask.
In order to achieve the aforementioned objects, the present invention takes the following aspects.
(First Aspect)
According to a first aspect of the present invention, there is provided an electron beam drawing mask blank comprising: a pattern supporting layer for transmitting an electron beam therethrough; an electron beam scattering layer formed over the pattern supporting layer; and a support member for supporting the pattern supporting layer and the electron beam scattering layer. The electron beam drawing mask blank is characterized in that the electron beam scattering layer is made of a material composed substantially of the carbon element and/or the silicon element.
(Second Aspect)
According to a second aspect of the present invention, the electron beam drawing mask blank in the first aspect is characterized in that the electron beam scattering layer is made of a material composed substantially of the carbon element.
(Third Aspect)
According to a third aspect of the present invention, the electron beam drawing mask blank in the second aspect is characterized in that the electron beam scattering layer is made of either a DLC or a material containing a DLC doped with at least one of B, N, Si and P.
(Fourth Aspect)
According to a fourth aspect of the present invention, the electron beam drawing mask blank in the third aspect is characterized in that the doping of the DLC with at least one of B, N, Si and P is 0.1 to 40 mole %
(Fifth Aspect)
According to a fifth aspect of the present invention, the electron beam drawing mask blank in the first aspect is characterized in that the electron beam scattering layer is made of a material composed substantially of the silicon element.
(Sixth Aspect)
According to a sixth aspect of the present invention, the electron beam drawing mask blank in any of the first to fifth aspects is characterized in that the pattern supporting layer is made of a material composed substantially of the carbon element.
(Seventh Aspect)
According to a seventh aspect of the present invention, the electron beam drawing mask blank in the sixth aspect is characterized in that the pattern supporting layer is made of either a DLC or a material containing a DLC doped with at least one of B, N, P, Ti, Si and Al.
(Eighth Aspect)
According to an eighth aspect of the present invention, the electron beam drawing mask blank in the seventh aspect is characterized in that the doping of the DLC with at least one of B, N, P, Ti, Si and Al is 0.1 to 40 mole %.
(Ninth Aspect)
According to a ninth aspect of the present invention, the electron beam drawing mask blank in any of the first to fifth aspects is characterized in that the pattern supporting layer is made of a material composed substantially of the silicon element.
(Tenth Aspect)
According to a tenth aspect of the present invention, the electron beam drawing mask blank in any of the first to ninth aspects further comprises an etching stopper layer sandwiched either between the electron beam scattering layer and the pattern supporting layer or between the pattern supporting layer and the support member.
(Eleventh Aspect)
According to an eleventh aspect of the present invention, the electron beam drawing mask blank in the tenth aspect is characterized in that the etching stopper layer is made of a material having a high etching selection ratio with the electron beam scattering layer and/or the support member.
(Twelfth Aspect)
According to a twelfth aspect of the present invention, the electron beam drawing mask blank in any of the first to eleventh aspects is characterized in that the support member is made of a material composed substantially of the carbon element.
(Thirteenth Aspect)
According to a thirteenth aspect of the present invention, there is provided an electron beam drawing mask blank comprising: a pattern supporting layer for transmitting an electron beam therethrough; an etching stopper layer formed over the pattern supporting layer; an electron beam scattering layer formed over the etching stopper layer; and a support member for supporting the pattern supporting layer, the etching stopper layer and the electron beam scattering layer. The electron beam drawing mask blank is characterized: in that the electron beam scattering layer is made of either a DLC or a material containing a DLC doped with at least one of B, N, Si and P; in that the pattern supporting layer is made of either a DLC or a material containing a DLC doped with at least one of B, N, P, Ti, Si and Al; and in that the etching stopper layer is made of a material having a high etching selection ratio with the electron beam scattering layer.
(Fourteenth Aspect)
According to a fourteenth aspect of the present invention, there is provided an electron beam drawing mask blank comprising: a pattern supporting layer (or an electron beam transmitting layer) for transmitting an electron beam therethrough; an electron beam scattering layer formed over the pattern supporting layer; and a support member for supporting the pattern supporting layer and the electron beam scattering layer. The electron beam drawing mask blank is characterized in that the pattern supporting layer has a film thickness of 0.005 to 0.2 micron whereas the electron beam scattering layer has a film thickness of 0.2 to 2 micron so that they are made of materials satisfying these film thickness relations.
(Fifteenth Aspect)
According to a fifteenth aspect of the present invention, the electron beam drawing mask blank in the fourteenth aspect is characterized in that the pattern supporting layer satisfies the following Formula (1):
Ttxe2x89xa62xcex1xe2x80x83xe2x80x83(1),
where Tt indicates the film thickness of the pattern supporting layer; and xcex1 indicates a mean free path of electrons in the pattern supporting layer.
(Sixteenth Aspect)
According to a sixteenth aspect of the present invention, the electron beam drawing mask blank in the sixteenth or fifteenth aspect is characterized in that the electron beam scattering layer satisfies the following Formula (2):
2xcex2xe2x89xa6Tsxe2x89xa610xcex2xe2x80x83xe2x80x83(2),
wherein: Ts indicates the film thickness of the electron beam scattering layer; and xcex2 indicates a mean free path of electrons in the electron beam scattering layer.
(Seventeenth Aspect)
According to a seventeenth aspect of the present invention, the electron beam drawing mask blank in any of the fourteenth to sixteenth aspects is characterized in that the pattern supporting layer and the electron beam scattering layer have film material densities of 1.0 to 5.0 g/cm3.
(Eighteenth Aspect)
According to an eighteenth aspect of the present invention, the electron beam drawing mask blank in any of the fourteenth to seventeenth aspects is characterized in that the pattern supporting layer and/or the electron beam an scattering layer have elastic moduli of 0.8xc3x971011 Pa or higher.
(Nineteenth Aspect)
According to a nineteenth aspect of the present invention, the electron beam drawing mask blank in any of the fourteenth to eighteenth aspects is characterized in that the pattern supporting layer and/or the electron beam scattering layer have a film thickness dispersion of 30% or less within one shot area.
(Twentieth Aspect)
According to a twentieth aspect of the present invention, the electron beam drawing mask blank in any of the fourteenth to nineteenth aspects is characterized in that the electron beam scattering layer is made of a material composed substantially of the carbon element and/or the silicon element.
(Twenty-first Aspect)
According to a twenty-first aspect of the present invention, the electron beam drawing mask blank in any of the fourteenth to twentieth aspects further comprises an etching stopper layer sandwiched either between the electron beam scattering layer and the pattern supporting layer or between the pattern supporting layer and the support member.
(Twent-second Aspect)
According to a twenty-second aspect of the present invention, the electron beam drawing mask blank in the twenty first aspect is characterized in that the etching stopper layer has a film thickness of 0.005 to 0.2 micron.
(Twenty-third Aspect)
According to a twenty-third aspect of the present invention, the electron beam drawing mask blank in the twenty first or twenty second aspects is characterized in that the etching stopper layer has a film material density of 1.0 to 5.0 g/cm3.
(Twenty-fourth Aspect)
According to a twenty-fourth aspect of the present invention, the electron beam drawing mask blank in any of the twenty first to twenty third aspects is characterized in that the etching stopper layer is made of a material having a high etching selection ratio with the electron beam scattering layer and/or the support member.
(Twenty-fifth Aspect)
According to a twenty-fifth aspect of the present invention, the electron beam drawing mask blank in any of the fourteenth to twenty fourth aspects is characterized in that at least one layer of the pattern supporting layer, the etching stopper layer and the electron beam scattering layer has a surface roughness (Ra) of 10 nm or lower.
(Twenty-sixth Aspect)
According to a twenty-sixth aspect of the present invention, the electron beam drawing mask blank in any of the fourteenth to twenty fifth aspects is characterized in that either at least one layer of the pattern supporting layer, the etching stopper layer and the electron beam scattering layer is stress-controlled by a heat treatment, or at least two layers are simultaneously subjected to a heat treatment to control the film stress thereby to reduce the total film stress.
(Twenty-seventh Aspect)
According to a twenty-seventh aspect of the present invention, an electron beam drawing mask is characterized in that it is manufactured by using the mask blank in any of the first to twenty sixth aspects.
(Twenty-eighth Aspect)
According to a twenty-eighth aspect of the present invention, there is provided an electron beam drawing mask comprising: pattern supporting film (or an electron beam transmitting film) for transmitting an electron beam therethrough; an electron beam scattering body pattern formed over the pattern supporting film; and a support member for supporting the pattern supporting film and the electron beam scattering body pattern. The electron beam drawing mask is characterized: in that the pattern supporting film has a film thickness of 0.005 to 0.2 micron, a film material density of 1.0 to 5.0 g/cm3 and an elastic modulus of 0.8xc3x971011 Pa or higher; and in that the electron beam scattering body pattern has a film thickness of 0.2 to 2 micron, a film material density of 1.0 to 5.0 g/cm3, and an elastic modulus of 0.8xc3x971011 Pa or higher.
(Twenty-ninth Aspect)
According to a twenty-ninth aspect of the present invention, there is provided an electron beam drawing mask comprising: an pattern supporting film (or an electron beam transmitting film) for transmitting an electron beam therethrough; an electron beam scattering body pattern formed over the pattern supporting film; and a support member for supporting the pattern supporting film and the electron beam scattering body patter. The electron beam drawing mask is characterized in that at least one of the support member, the pattern supporting film and the electron beam scattering body pattern is made of a material composed substantially of the carbon element.
(Thirtieth Aspect)
According to a thirtieth aspect of the present invention, there is provided an electron beam drawing mask comprising: a pattern supporting film (or an electron beam transmitting film) for transmitting an electron beam therethrough; an electron beam scattering body pattern formed over the pattern supporting film; an etching stopper layer formed all over the pattern supporting film or left under the electron beam scattering body pattern; and a support member for supporting the pattern supporting film, the etching stopper layer and the electron beam scattering body pattern. The electron beam drawing mask is characterized: in that the electron beam scattering body pattern is made of either a DLC or a material containing a DLC doped with at least one of B, N, Si and P; in that the pattern supporting film is made of either a DLC or a material containing a DLC doped with at least one of B, N, P, Ti, Si and Al; and in that the etching stopper layer is made of a material having a high etching selection ratio with the electron beam scattering layer.
(Thirty-first Aspect)
According to a thirty-first aspect of the present invention, there is provided an electron beam drawing mask comprising: a pattern supporting film (or an electron beam transmitting film) for transmitting an electron beam therethrough; an electron beam scattering body pattern formed over the pattern supporting film; and a support member for supporting the pattern supporting film and the electron beam scattering body pattern. The electron beam drawing mask is characterized in that: the electron beam scattering body pattern is made of a material composed substantially of the silicon element; and in that the pattern supporting film is made of SiC or TiC.
(Thirty-second Aspect)
According to a thirty-second aspect of the present invention, there is provided an electron beam drawing mask comprising: a pattern supporting film (or an electron beam transmitting film) for transmitting an electron beam therethrough; an etching stopper layer formed over the pattern supporting film; an electron beam scattering body pattern formed over the etching stopper layer; and a support member for supporting the pattern supporting film, the etching stopper layer and the electron beam scattering body pattern. The electron beam drawing mask is characterized: in that the electron beam scattering body pattern is made of hard carbon; in that the etching stopper layer is made of SiO2; and in that the pattern supporting film is made of a material composed substantially of the silicon element.
(Thirty-third Aspect)
According to a thirty-third aspect of the present invention, there is provided an electron beam drawing mask comprising: a pattern supporting film (or an electron beam transmitting film) for transmitting an electron beam therethrough; an electron beam scattering body pattern formed over the pattern supporting film; and a support member for supporting the pattern supporting film and the electron beam scattering body pattern. The electron beam drawing mask is characterized: in that the electron beam scattering body pattern is made of either a DLC or a material containing a DLC doped with at least one of B, N, Si and P; in that the pattern supporting film is made of xcex2-SiC.
(Thirty-fourth Aspect)
According to a thirty-fourth aspect of the present invention, there is provided an electron beam drawing mask comprising: a pattern supporting film (or an electron beam transmitting film) for transmitting an electron beam therethrough; an electron beam scattering body pattern formed over the pattern supporting film; and a support member for supporting the pattern supporting film and the electron beam scattering body pattern. The electron beam drawing mask is characterized: in that the electron beam scattering body pattern is made of a material composed substantially of the silicon element; and in that the pattern supporting film is made of SiC.
(Thirty-fifth Aspect)
According to a thirty-fifth aspect of the present invention, there is provided an electron beam drawing mask comprising: a pattern supporting film (or an electron beam transmitting film) for transmitting an electron beam therethrough; an electron beam scattering body pattern formed over the pattern supporting film; and a support member for supporting the pattern supporting film and the electron beam scattering body pattern. The electron beam drawing mask is characterized: in that the electron beam scattering body pattern is made of a material composed substantially of the silicon element; and in that the pattern supporting film is made of either a DLC or a material containing a DLC doped with at least one of B, N, P, Ti, Si and Al.
(Thirty-sixth Aspect)
According to a thirty-sixth aspect of the present invention, the electron beam drawing mask in any of the twenty seventh to thirty fifth aspects is characterized in that the electron beam drawing mask is used at an acceleration voltage of an exposure electron beam of 30 KeV or higher.
(Thirty-seventh Aspect)
According to a thirty-seventh aspect of the present invention, there is provided a method for manufacturing an electron beam drawing mask, characterized by comprising the step of forming at least one of a compressive stress film and a tensile stress film on the surface side or back side of the electron beam drawing mask in any of the twenty seventh to thirty sixth aspects.
(Thirty-eighth Aspect)
According to a thirty-eighth aspect of the present invention, there is provided a method for manufacturing an electron beam drawing mask, characterized by comprising the steps of: subjecting an SIMOX wafer or an adhered SOI wafer to a wind treatment from the back side; subsequently removing a stopper layer (or an intermediate layer) in the water selectively; and forming a pattern supporting film (or an electron beam transmitting film) on one side from the back side by a thin film forming method.
(Thirty-ninth Aspect)
According to a thirty-ninth aspect of the present invention, there is provided a semiconductor device characterized in that it is manufactured by using an electron beam drawing mask in any of the twenty seventh to thirty sixth aspects.
According to the foregoing first aspect, there can be attained the following effects. Where the electron beam scattering layer is made of a material composed substantially of a metallic element such as Mo or W as in the SCALPEL of the prior art, as has been described hereinbefore, the pattern supporting layer (of SiN or the like) having the minimum necessary film thickness is required for supporting the electron beam scattering layer. However, this requirement causes a problem that the resolution is deteriorated by the color aberration resulting from the energy loss or energy dispersion in the pattern supporting layer. According to the first aspect, on the other hand, the electron beam scattering layer is made of the xe2x80x9cmaterial composed substantially of the carbon element and/or the silicon elementxe2x80x9d, so that the film thickness of the pattern supporting layer can be reduced to lighten the aforementioned problems. Here, the xe2x80x9cmaterial composed substantially of the carbon element and/or the silicon elementxe2x80x9d covers the case in which the material contains one kind or two or more kinds of B, P, H, N, O and halogens and the case in which the material is doped additionally or solely with a trace amount of metallic element.
According to the second aspect, the electron beam scattering layer in the first aspect is limited to the case in which it is made of a xe2x80x9cmaterial composed substantially of the carbon elementxe2x80x9d. Here, the xe2x80x9cmaterial composed substantially of the carbon elementxe2x80x9d is desired to be such a material as has a component having a low film material density and high material strength characteristics such as the Young""s modulus and capable of making the electron beam scattering body as thick as possible, as is excellent in the chemical resistance and the irradiation resistance and as can be excellently etched from the viewpoint of the pattern precision. In addition, the xe2x80x9cmaterial composed substantially of the carbon elementxe2x80x9d is preferably other than the insulating material while considering the charge. The material satisfying the above-specified characteristics is exemplified by diamond, diamond like carbon (DLC) or hard carbon. The film of these materials can contain nitrogen, boron, silicon or phosphor.
The third aspect limits the electron beam scattering layer in the second aspect to the case in which it is made of the xe2x80x9cthe DLC or the DLC doped with at least one of B, N, Si and Paxe2x80x9d. By this doping the DLC with at least one of B, N, Si and P, the DLC can be given a conductivity to avoid the influence of the charging or the like. The DLC constructing the electron beam scattering layer is preferred to have a film thickness of about 300 to 700 nm.
In the fourth aspect, if the doping of the DLC with at least one of B, N, Si and P exceeds 40 mole %, it may occur that the properties of the DLC film or the etching selectivity are deteriorated. If the doping is less than 0.1 mole %, on the other hand, it may occur that the effects of giving the conductivity by the doping or the reducing the film resistance are not sufficient.
According to the fifth aspect, the electron beam scattering layer in the first aspect is limited to the case in which xe2x80x9cit is made of a material composed substantially of the silicon elementxe2x80x9d. Here, the xe2x80x9cmaterial composed substantially of the silicon elementxe2x80x9d is exemplified by amorphous silicon, polycrystalline silicon or single crystal silicon. These materials may be individually doped with B or P.
According to the sixth aspect, the pattern supporting layer in the first to fifth aspects is limited to the case in which xe2x80x9cit is made of a material composed substantially of the carbon elementxe2x80x9d. Here, the xe2x80x9cmaterial composed substantially of the carbon elementxe2x80x9d is desired to be such a material as has a component having a low film material density and high material strength characteristics such as the Young""s modulus and capable of making the electron beam scattering body as thick as possible, as is excellent in the chemical resistance and the irradiation resistance and as can be excellently etched from the viewpoint of the pattern precision. In addition, the xe2x80x9cmaterial composed substantially of the carbon elementxe2x80x9d is preferably other than the insulating material while considering the charge. The material satisfying the above-specified characteristics is exemplified by diamond, diamond like carbon (DLC) or hard carbon. The film of these materials can contain nitrogen, boron, silicon or phosphor.
According to the seventh aspect, the pattern supporting layer in the sixth aspect is limited to the case in which xe2x80x9cit is made of a material of the DLC or the DLC doped with at least one of B, N, P, Ti, Si and Alxe2x80x9d. Here, by doping the DLC with at least one of B, N, P, Ti, Si and Al, the DLC can be given the conductivity to avoid the influence of the charging or the like.
According to the eighth aspect, if the doping of the DLC with at least one of B, N, P, Ti, Si and Al exceeds 40 mole %, it may occur that the properties of the DLC film or the etching selectivity is deteriorated. If the doping is less than 0.1 mole %, on the other hand, it may occur that the effects of giving the conductivity by the doping or reducing the film resistance cannot be sufficiently obtained.
Here will be described the reasons why the elements the DLC is to be doped are different between the electron beam scattering layer in the third aspect and the pattern supporting layer in the eighth aspect. The electron beam scattering layer has to be etched to form the pattern so that the doping element is restricted not to deteriorate the etching characteristics. For the pattern supporting layer, on the other hand, a wider range of doping elements can be selected for improving the mechanical strength. If the DLC making the electron beam scattering layer is doped with the Ti or Al which is accepted by the pattern supporting layer, it unpreferably forms a film which is hard to etch.
According to the ninth aspect, the pattern supporting layer in the first to fifth aspects is limited to the case in which xe2x80x9cit is made of a material composed substantially of the silicon elementxe2x80x9d. Here, the xe2x80x9cmaterial composed substantially of the silicon elementxe2x80x9d is exemplified by amorphous silicon, polycrystalline silicon or single crystal silicon. These materials may be individually doped with B or P.
According to the tenth aspect, the etching stopper layer is sandwiched between the electron beam scattering layer and the pattern supporting layer so that the pattern supporting layer can be prevented from being etched when the electron beam scattering layer is etched to form the pattern, thereby to enhance the margin at the working time. After the pattern formation, on the other hand, the film stress balance of the pattern region can be made to provide a stabler mask. Here, after the pattern formation, the etching stopper layer to be exposed from the opening of the electron beam scattering layer may or may not be removed.
When the support member is to be etched from the back side, on the other hand, the etching stopper layer is sandwiched between the pattern supporting layer and the support member so that the pattern supporting layer can be prevented from being etched from the back side, to enhance the margin at the working time. After the pattern was formed on the electron beam scattering layer, on the other hand, the film stress balance of the pattern region can be adjusted to provide a stabler mask.
Here, the etching stopper layers of the aforementioned two kinds may be made of an identical material or different materials.
Here in the mask blank according to the present invention, the support member covers both the substrate made of the support member material and the support member which is obtained by working the substrate of the support member material from the back side. This applied to the first to twenty sixth aspects.
As defined in the eleventh aspect, the etching stopper layer is preferably made of a material having a high etching selection ratio to the electron beam scattering layer and/or the support member. At the higher etching selection ratio, the electron beam scattering layer and/or the support member can be more prevented from being etched. The material for the etching stopper layer is exemplified by SiC, TiC, TiN, amorphous Si, Ti, Al or SiO2. The etching stopper layer has a film thickness preferably of 0.005 to 0.2 micron and more preferably of about 10 to 20 nm.
As defined in the twelfth aspect, the support member is made of a material composed substantially of the carbon element to make such an etching possible as having an extremely high etching selectivity of 100 or higher with respect to the etching stopper layer or the like. As a result, the material selectivity can be widened to make the etching stopper layer remarkably thin thereby to provide an ideal mask blank with a surplus workability.
In the thirteenth aspect, by making the individual layers of the materials as presented in the thirteenth aspect, it is easy to improve the etching selectivity, i.e., to retain the process margin. Since a laminated structure of materials of similar kinds is made through the etching stopper layer, on the other hand, the material characteristics are so similar that the coefficient of thermal expansion and the thermal conductivity can be made similar. As a result, it is possible to suppress the dispersion of the thermal distortion. Moreover, the working conditions such as the etching condition can be easily selected.
By this doping the DLC with at least one of B, N, Si and P, the DLC can be given a conductivity to avoid the influence of the charging or the like. The DLC constructing the electron beam scattering layer is preferred to have a film thickness of about 300 to 700 nm.
Here, the DLC making the pattern supporting layer can be doped with at least one of B, N, P, Ti, Si and Al thereby to give the DLC the conductivity and the tensile stress. The DLC making the pattern supporting layer preferably has a film thickness of about 30 to 80 nm.
The etching stopper layer is similar to that of the eleventh aspect.
Here, the method of doping the DLC making the pattern supporting layer and the DLC making the electron beam scattering layer with another element is exemplified by the method of doping the filmed DLC by the ion implantation method. For this method, however, facilities dedicated to the ion implantation have to be introduced. From the viewpoint of simplifying the process or the like, the preferable method is to dope the DLC being filmed with another element.
Here, the DLC making the pattern supporting layer and the DLC making the etching stopper layer and the electron beam scattering layer are preferred to be continuously filmed because it is possible to reduce the particles.
If the DLC making the pattern supporting layer and the DLC making the electron beam scattering layer are filmed by the film forming method of excluding hydrogen therefrom, on the other hand, the thermal conductivity is preferably improved (better than the excellent thermal conductivity of the single crystal Si). The film forming method of this known kind is exemplified by the negative ion beam sputtering method, the opposed target sputtering method or the ECR-sputtering method. If hydrogen is contained in the DLC, the trailing end of the diamond bond is terminated to cut the network structure of the film. This unpreferably lowers the thermal conductivity characteristics and the Young""s modulus.
From the requirement for the material satisfying the predetermined film thickness relation, the fourteenth aspect excludes the case in which the electron beam scattering layer is made of a heavy metal. This is because the mask made of the materials satisfying the aforementioned film thickness relation cannot be realized where the electron beam scattering layer is made of the heavy metal. It follows that there is excluded the mask having the construction in which the metallic electron beam scattering layer of W or Mo is supported by the pattern supporting layer, such as the SCALPEL mask of the prior art.
The exposure electron beam loss depends substantially on the film thickness and the film material density of the pattern supporting layer. The exposure electron loss (%) is determined from the following Formula:
(1xe2x88x92exe2x88x92(Tt/xcex1)xc3x97100,
wherein: Tt indicates the film thickness of the pattern supporting layer; and xcex1 indicates the mean free path of the electrons in the pattern supporting layer. On the other hand, (Tt/xcex1) indicates the film thickness for the electrons to scatter one time.
As the film material density grows the higher, the mean free path a becomes the smaller, and the exposure electron loss also becomes the smaller.
Where the film material density is 1 g/cm3, the exposure electron loss is about 45% if the film thickness is 0.2 micron. If the film thickness of the pattern supporting layer exceeds 0.2 micron, therefore, one half or more of the exposure electrons will be lost to deteriorate the exposure efficiency impractically.
On the other hand, a deflection xcex4 of the pattern supporting layer has to be within xcex4xe2x89xa6DOF (focal depth). For a DOF of 2 to 3 micron, the deflection xcex4 is determined from the following Formula:
xcex4=(kxc3x97Wxc3x97a4)/(Exc3x97Tt3)xe2x89xa62 (micron),
wherein: k indicates a (known) deflection coefficient; W indicates a force (or known as its own weight) to act on the film; a indicates a (known) length of one side of the pattern field; and E indicates the Young""s modulus of the pattern supporting layer.
In order to reduce the deflection xcex4, therefore, it is sufficient to enlarge the term (Exc3x97Tt3).
Here, the letter E indicates the Young""s modulus (the maximum: 500 GPa for the film material) of the DLC. Then, it is difficult to make the deflection xcex4 no more than 2 micron if the pattern supporting layer has a film thickness of 0.005 micron or more.
Where the pattern supporting layer has a thickness less than 0.005 micron, on the other hand, it cannot sufficiently support the electron beam scattering layer formed thereover, so that a sufficient film stability cannot be obtained. Moreover, the dislocation of the pattern position may be invited by the change, as may be caused at the time of etching the electron beam scattering layer, in the stress distribution in the vicinity of the pattern.
The pattern supporting layer has preferably a thickness of 0.005 to 0.2 micron, more preferably a thickness of 0.005 to 0.1 micron, and more preferably a thickness of 0.01 to 0.05 micron.
Where the electron beam scattering layer has a thickness less than 0.2 micron, as made of a light element, the scattering number of electrons in the electron beam scattering layer is not so sufficient that a satisfactory beam contrast cannot be achieved. In the case of the leaf pattern, on the other hand, a sufficient film self-sustainability cannot be achieved. If the thickness of the electron beam scattering layer exceeds 2 micron, on the other hand, the scattering number of electrons in the electron beam scattering layer is so large that the control of the scattering angle of electrons may become difficult. With the difficulty in the control of the scattering angle of electrons, the electron scattering angle distribution becomes too large, when auxiliary exposure means such as the GHOST method is adopted to correct the proximity effect, to perform a satisfactory auxiliary exposure. For the electron beam scattering layer, on the other hand, a fine pattern is formed by the anisotropic dry-etching method, for example. As the etching depth of the electron beam scattering layer becomes the larger, however, there impreferably arises the tendency to deteriorate the working precision of the electron beam scattering layer. This electron beam scattering layer has a preferable thickness range of 0.3 to 1.5 micron.
When both the pattern supporting layer and the electron beam scattering layer have film thicknesses within the above-specified ranges, the film stability is kept for the mask. On the other hand, the transmission and the scattering of electrons can be controlled to improve the throughput at the exposure time.
According to the fifteenth aspect, if the pattern supporting layer satisfies the following Relation (1), it is possible to suppress the scattering of electrons thereby to lower the exposure electron loss and to improve the exposure efficiency:
Ttxe2x89xa62xcex1xe2x80x83xe2x80x83(1).
Preferably Ttxe2x89xa6xcex1
In the sixteenth aspect, where the film thickness is less than 2xcex2, i.e., where the electron beam scattering layer does not have such a film thickness as to allow at least two times of electron scattering, it is impossible to achieve a satisfactory beam contrast on the wafer. If the film thickness exceeds 10xcex2, on the other hand, the scattering times of electrons in the electron beam scattering layer may become so many as to make it difficult to control the scattering angle of electrons. In the difficulty to control the scattering angle, the electron scattering angle distribution becomes so large, when the auxiliary exposure means such as the GHOST method is adopted to make the proximity effect correction, as to make it difficult to perform a satisfactory auxiliary exposure. For the electron beam scattering layer, on the other hand, the fine pattern is formed by the anisotropic dry-etching method, for example. As the etching depth grows the deeper, however, there arises a tendency to deteriorate the working precision, and it is not preferable to make the electron beam scattering layer thicker than 10xcex2.
In the seventeenth aspect, the xe2x80x9cfilm material densityxe2x80x9d means that the density of the material itself making the pattern supporting layer or the electron beam scattering layer.
In the case of the pattern supporting layer, the probability for the electrons to transmit through the pattern supporting layer without any dispersion is expressed by the following Formula:
exe2x88x92(Tt/xcex1).
As the film material density grows the higher, the mean free path xcex1 becomes the smaller. In order to achieve a desired exposure electron amount, therefore, the film thickness of the pattern supporting layer has to be reduced so as to enhance the probability exe2x88x92(Tt/xcex1) for the electrons to pass through the pattern supporting layer without any dispersion.
However, the film thickness has to be within the range (0.005 to 0.2 micron) defined in the fourteenth aspect. For this necessity, the film material density of the pattern supporting layer has an upper limit of 5.0 g/cm3 and a lower limit of 1.0 g/cm3.
In the case of the electron beam scattering layer, several or more scattering operations are necessary for a beam contrast of 90% or higher. In this case, in dependence upon the material density, the film thickness for one scattering changes so that it can be made the smaller for the higher material density. For the lower material density, on the contrary, the film thickness becomes the larger. As described above, moreover, the film thickness has to be within the range (0.2 to 2 micron) defined in the fourteenth aspect, so that the film material density of the electron beam scattering layer has the upper limit of 5.0 g/cm3 and the lower limit of 1.0 g/cm3.
Since both the film material density of the pattern supporting layer and the electron beam scattering layer are within the above-specified ranges, the individual films have the self-sustainability. Unlike the construction that the electron beam scattering layer made of the metal such as W or Mo is supported by the electron beam transmitting layer like the SCALPEL mask of the prior art, therefore, no deflection occurs in the individual layers themselves and between the layers in the case of the present invention. Even if the electron beam scattering layer is etched to form the patter, on the other hand, the pattern position change is hardly invited because of the small deflection change.
In the eighteenth aspect, if the elastic moduli of the pattern supporting layer and the electron beam scattering layer are individually less than 0.8xc3x971011 Pa, the individual films may be unable to keep their self-sustainabilities to fail to form the stable mask.
From the viewpoint of the mask stability, it is preferable that the elastic moduli of both the pattern supporting layer and the electron beam scattering layer are 0.8xc3x971011 Pa or higher, and it is more preferable that the same are 1.0xc3x971011 Pa or higher.
In the nineteenth aspect, i the dispersion of the film thickness in the one-shot area of the pattern supporting layer exceeds 30% with respect to the set film thickness, the dispersion of the exposure electron amount may become large to invite the deterioration in the exposure characteristics. The dispersion of the film thickness of the pattern supporting layer is preferable to be less than xc2x110%.
If the dispersion of the film thickness of the electron beam scattering layer exceeds 30%, the scattering angle of electrons may become difficult to control thereby to perform the auxiliary exposure effectively. On the other hand, the precision may be influenced in the patterning by the etching. The dispersion of the film thickness of the electron beam scattering layer is more preferable to be less than xc2x110%.
According to the twentieth aspect, there are obtained the following effects. Where the electron beam scattering layer is made of a material composed substantially of a metallic element such as Mo or W as in the SCALPEL mask of the prior art, it has to be supported by the pattern supporting layer (of SiN or the like) having the minimum necessary film thickness for the support. However, there arises a problem that the resolution is degraded by the color aberration resulting from the energy loss or energy dispersion in the pattern supporting layer. By making the electron beam scattering layer of a xe2x80x9cmaterial composed substantially of the carbon element and/or the silicon elementxe2x80x9d as in the twentieth aspect, however, the film thickness of the pattern supporting layer can be reduced to diminish the aforementioned problems.
Here, the xe2x80x9cmaterial composed substantially of the carbon element and/or the silicon elementxe2x80x9d covers the case in which the material contains one kind or two or more kinds of B, P, H, N, O and halogens and the case in which the material is doped additionally or solely with a trace amount of metallic element.
The xe2x80x9cmaterial composed substantially of the carbon elementsxe2x80x9d is desired to be such a material as has a component having a low film material density and high material strength characteristics such as the Young""s modulus and capable of making the electron beam scattering body as thick as possible, as is excellent in the chemical resistance and the irradiation resistance and as can be excellently etched from the viewpoint of the pattern precision. In addition, the xe2x80x9cmaterial composed substantially of the carbon elementxe2x80x9d is preferably other than the insulating material while considering the charge. The material satisfying the above-specified characteristics is exemplified by diamond, diamond like carbon (DLC) or hard carbon. The film of these materials can contain nitrogen, boron, silicon or phosphor.
The xe2x80x9cmaterial composed substantially of the silicon elementxe2x80x9d is exemplified by amorphous silicon, polycrystalline silicon or single crystal silicon. These materials may be individually doped with B or P.
In the twenty-first aspect, the etching stopper layer is sandwiched between the electron beam scattering layer and the pattern supporting layer so that the pattern supporting layer can be prevented from being etched when the electron beam scattering layer is etched to form the pattern, thereby to enhance the margin at the working time. After the pattern formation, on the other hand, the film stress balance of the pattern region can be made to provide a stabler mask. Here, after the pattern formation, the etching stopper layer to be exposed from the opening of the electron beam scattering layer may or may not be removed.
When the support member is to be etched from the back side, on the other hand, the etching stopper layer is sandwiched between the pattern supporting layer and the support member so that the pattern supporting layer can be prevented from being etched from the back side, to enhance the margin at the working time. After the pattern was formed on the electron beam scattering layer, on the other hand, the film stress balance of the pattern region can be adjusted to provide a stabler mask.
Here, the etching stopper layers of the aforementioned two kinds may be made of an identical material or different materials.
In the twenty-second aspect, if the film thickness of the etching stopper layer is less than 0.005 micron, a sufficient etching stopper effect cannot be expected. If the film thickness exceeds 0.2 micron, on the other hand, the deflection of the pattern region may be invited by the action of the film stress of the etching stopper layer itself.
In the twenty-third aspect, the reason for the limitation of the film material density in the etching stopper layer is similar to that in the pattern supporting layer mentioned in relation to the seventeenth aspect.
In the twenty-fourth aspect, the etching stopper layer is sandwiched between the electron beam scattering layer and the pattern supporting layer so that the pattern supporting layer can be prevented from being etched when the electron beam scattering layer is etched to form the pattern, thereby to enhance the margin at the working time. After the pattern formation, on the other hand, the film stress balance of the pattern region can be made to provide a stabler mask. Here, after the pattern formation, the etching stopper layer to be exposed from the opening of the electron beam scattering layer may or may not be removed.
When the support member is to be etched from the back side, on the other hand, the etching stopper layer is sandwiched between the pattern supporting layer and the support member so that the pattern supporting layer can be prevented from being etched from the back side, to enhance the margin at the working time. After the pattern was formed on the electron beam scattering layer, on the other hand, the film stress balance of the pattern region can be adjusted to provide a stabler mask.
Here, the etching stopper layers of the aforementioned two kinds may be made of an Identical material or different materials.
In the twenty-fifth aspect, the surface roughness (Ra) of each layer is made no more than 10 nm. This is because the edge roughness characteristics of the mask pattern such as the electron beam scattering pattern and the exposures are adversely affected if those layers have the rough surfaces. As one reason, more specifically, it the surfaces of the layers underlying the resist layer are rough at the resist pattern formation of mask manufacturing time, the edge roughness characteristics of the resist pattern may be deteriorated by the secondary electrons coming from those layers. Still the worse, the side walls of the electron beam scattering pattern are roughed to adversely affect the edge roughness of the mask pattern.
As another reason, the pattern supporting layer (may include the etching stopper layer) is so thin (at about 50 nm) that the surface roughness at the level of 5 nm or 10 nm causes a local film thickness roughness. This film thickness dispersion causes an excessive electron scattering in the portion of the electron beam scattering body so that the exposure pattern shape is deteriorated by the stored charge effect at the electron beam scattering body pattern portion.
In order to suppress the exposure dispersion within 5% at the real transfer time, the exposure electron distribution in one shot has to be made better. In the film material of the present invention, about 60 to 80% of the electrons incident on the mask contribute as the exposure electrons. The remaining about 30% is cut. Where the surface roughness is 10 nm for the thickness of 50 nm of the pattern supporting layer, for example, it corresponds to the film thickness dispersion of about 20% with respect to the film thickness. With a large film thickness dispersion, there is enlarged the dispersion of the ratio of the exposure electrons and accordingly the exposure dispersion at the real exposure time.
The local dispersion in one shot cannot be basically corrected so that the surface roughness has a high influence. In order that the influences of the surface roughnesses of the individual layers may be reduced more, the surface roughnesses of the individual layers are preferably no more than 5 nm and more preferably no more 2 nm.
In relation to the line width of the electron beam scattering body pattern, the surface roughness of the etching stopper layer or the pattern supporting layer is preferred to be no more than {fraction (1/100)} of the line width of the electron beam scattering pattern. Where the electron beam scattering pattern has a line width no more than 0.2 micron, more specifically, the surface roughness of the etching stopper layer or the pattern supporting layer is preferred to be no more than 2 nm. Thus, the aforementioned problems can be solved.
Where the pattern supporting layer and the electron beam scattering layer are made of the DLC, for example, the surface roughnesses (Ra) of the pattern supporting layer and the electron beam scattering layer can be made no more than 2 nm by selecting and controlling the film forming method and the film forming conditions.
The pattern supporting layer is preferably made of a material having a high Young""s modulus because it is required to have the film self-sustainability. For example, the diamond film has a high Young""s modulus (i.e., 500 GPa). However, it is difficult to make the surface roughness of the diamond film no more than 2 nm and accordingly to avoid the aforementioned influences of the surface roughness. It is conceivable to polish and smooth the diamond film after filmed. However, the diamond is an extremely hard material to have a poor polishing efficiency, and its film is easily damaged even polished so that it has a poor practical value.
Here, an excessive electron scattering occurs in the electron beam scattering layer, too, and the exposure pattern shape is deteriorated by the storage charge effect at the electron beam scattering body pattern portion. Thus, the surface roughness is preferably 10 nm or less.
According to the twenty-sixth aspect, the stresses of the individual layers can be subjected individually or altogether to a heat treatment (or annealed) to lower the total film stress. The atmosphere for this heat treatment is preferably exemplified by the vacuum which is established by evacuating it in a vacuum apparatus, or by the atmosphere which is evacuated and then supplied in the vacuum apparatus with an inert gas such as He or Ar or at least one kind of the gases of H2, N2 and so on.
The heat treatment temperature is suitably selected from a proper temperature range in terms of the in-film hydrogen concentration, but is preferred for the case of the DLC to be higher by 200 to 450xc2x0 C. than the substrate temperature at the DLC film forming time.
According to the twenty-seventh aspect, if the mask is manufactured by using the aforementioned mask blank according to the present invention, it is possible to provide an electron beam drawing mask which is excellent in the structural characteristics, the manufacturing characteristics and the lithography required characteristics.
According to the twenty-eighth aspect, if the film thicknesses, the film material densities and the elastic moduli of the pattern supporting layer and the electron beam scattering layer are specified, it is possible to provide an electron beam drawing mask which is excellent in the structural characteristics, the manufacturing characteristics and the lithography required characteristics.
According to the twenty-ninth aspect, if at least one of the support member, the pattern supporting film and the electron beam scattering body pattern layer is made of a material composed substantially of the carbon element such as the DLC or the hard carbon, it is possible to provide an electron beam drawing mask which is excellent especially in the structural characteristics, the manufacturing characteristics and the lithography required characteristics.
According to the thirtieth aspect, by making the individual layers of the materials specified in the thirtieth aspect, it is easy to improve the etching selectivity, i.e., to retain the process margin. On the other hand, the laminated structure of similar materials is obtained through the etching stopper layer so that the material characteristics resemble. As a result, the thermal expansion coefficients, the thermal conductivities and so on can be made similar so that the dispersion can be suppressed against the thermal distortion. Moreover, it is easy to select the working conditions such as the etching conditions.
As has been described hereinbefore, the DLC making the electron beam scattering pattern can be doped with at least one of B, N, Si and P. As a result, the DLC can be given the conductivity to avoid the mask charging influences. The DLC making the electron beam scattering body pattern is preferred to have a film thickness of about 300 to 700 nm.
The etching stopper layer is preferably made of a material hard to etch with an acidic gas so that it may etch the DLC making the electron beam scattering body pattern with the oxidizing gas. This material is exemplified by SiC, TiC, TiN, amorphous Si, Ti and Al. The etching stopper layer has a film thickness preferably of 0.005 to 0.2 micron and more preferably of about 10 to 20 nm. Where the etching stopper layer is left below the electron beam scattering body pattern, the exposed etching stopper layer may be etched off after the electron beam scattering body pattern was formed.
The DLC making the pattern supporting film can be doped with at least one of B, N, P, Ti, Si and Al so that the DLC can be given the conductivity and the tensile stress. The DLC making the pattern supporting film has a film thickness preferably of about 30 to 80 nm.
Here, the method of doping the DLC making the pattern supporting film and the DLC making the electron beam scattering body pattern with another element is exemplified by the method of doping the filmed DLC by the ion implantation method. For this method, however, facilities dedicated to the ion implantation have to be introduced. From the viewpoint of simplifying the process or the like, the preferable method is to dope the DLC being filmed with another element.
Here, the DLC making the pattern supporting film and the DLC making the etching stopper layer and the electron beam scattering body pattern are preferred to be continuously filmed because it is possible to reduce the particles.
If the DLC making the pattern supporting film and the DLC making the electron beam scattering body pattern are filmed by the film forming method of excluding hydrogen therefrom, on the other hand, the thermal conductivity is preferably improved (better than the excellent thermal conductivity of the single crystal Si). The film forming method of this known kind is exemplified by the negative Ion beam sputtering method, the opposed target sputtering method or the ECR-sputtering method. If hydrogen is contained in the DLC, the trailing end of the diamond bond is terminated to cut the network structure of the film. This unpreferably lowers the thermal conductivity characteristics and the Young""s modulus.
The thirty-first to thirty-fifth aspects are presented to exemplify the mask construction of the embodiments to be described hereinafter. The thirty-first aspect presents the mask construction of Embodiment 1; the thirty-second aspect presents the mask construction of Embodiment 2; the thirty-third aspect presents the mask construction of Embodiment 3; the thirty-fourth aspect presents the mask construction of Embodiment 4; and the thirty-fifth aspect presents the mask construction of Embodiment 6.
Here in the thirty-first, thirty-second, thirty-fourth and thirty-fifth aspects, the material composed substantially of the silicon element is exemplified by amorphous silicon, polycrystalline silicon or single crystal silicon. These materials may be individually doped with B or P.
The thirty-sixth aspect regulates the specifications of the electron beam drawing mask on the acceleration voltage of the exposure electron beam. For different specifications of the acceleration voltage, the required characteristics for the mask are naturally different The mask satisfying these specifications can be employed at the high acceleration voltage in the SCALPEL system, for example.
According to the thirty-seventh aspect, there is provided a method for manufacturing an electron beam drawing mask, characterized by comprising the step of forming at least one of a compressive stress film and a tensile stress film on the surface side or back side of the electron beam drawing mask in any of the twenty-seventh to thirty-sixth aspects. As a result, the stress balance of the pattern region can be controlled after the mask was manufactured.
According to the thirty-eighth aspect, there is provided a method for manufacturing an electron beam drawing mask, characterized by comprising the steps of: subjecting an SIMOX wafer to a wind treatment from the back side; subsequently removing the stopper SiO2 layer in the SIMOX wafer selectively; and forming a pattern supporting film from the back side by the thin film forming method. It follows that the thickness of the pattern supporting film can be freely adjusted. Another advantage is that the Si single crystal layer excellent in the dry-etching properties can be used in the electron beam scattering body.
According to the thirty-ninth aspect, by using the electron beam drawing mask according to the present invention, the throughput at the exposure time can be improved to provide a semiconductor device such as a superhigh integrated circuit or a semiconductor element at a low cost.